Telnet and the differences between local and remote login




The main task of the Internet and TCP?IP protocol is to provide services for the users.when a user wants to run different application programs at a remote site,he can try two solutions.one is to create different client-server application programs.It is impossible to write a specific client-server program for each demand.So,we go for another solution which allows the user to log on to a remote computer.After logging on,user can use the services available on the remote computer and transfer the results back to the local computer.

Telnet is known as TERMINAL NETWORK which is a client-server application program.It enables the establishment of a connection to a remote system in such a way that the local terminal appears to be a terminal at the remote system.
we have two types of login here.They are

*LOCAL LOGIN
*REMOTE LOGIN

LOCAL LOGIN:
When a user logs into a local time-sharing program,it is local login.As a user types at a terimal running a terminal emulator,the keystrokes are accepted by the terminal driver.The terminal driver passes the characters to the operating system.The operating system may assign special meanings to characters.These situations do not create any problem in local login because the terminal emulator and the terminal driver know the exact meaning of each character ,they may create problems in remote login.

REMOTE LOGIN:
when a user wants to access an application program,he or she perfroms remote login.The user sends keystrokes to the terminal driver where the local operating system accepts the characters but they wont interpret them.They are sent to TELNET CLIENT,which in turn transforms the characters to a universal character set called "Network Virtual terminal characters" and delivers them to local TCP/IP stack.However,characters cant be passed directly to the operating system because remote operating system is not designed to receive characters from TELNET SERVER.It is designed such that it receives characters from TERMINAL DRIVERS.The solution for this is to add a piece of software called a Pseudoterminal driver,which pretends that the characters are coming from a terminal.The operating system passes the characters to appropriate application programs.


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